In order to recover natural resources from underwater subterranean formations it is often necessary to perform exploration, monitoring, maintenance and construction operations on or beneath the sea floor. In relatively shallow depths these tasks can be performed by divers. However, at greater depths, and also when conditions are dangerous at shallow depths, the tasks are generally performed by robotic devices. Various types of robotic devices are known. For example, a remotely operated vehicle (ROV) is a robotic device that functions under the control of an operator via an umbilical cable that connects the ROV with a surface ship. A somewhat similar device, known as an autonomous underwater vehicle (AUV), operates according to programming, without physical connection to a surface ship. Hybrid ROVs which can operate either autonomously or via a physical connection to a surface ship are also known. Generally, ROVs are characterized by relatively limited range because of the physical connection to the surface ship. However, an ROV can operate indefinitely because energy is supplied by the surface ship. ROVs traverse the subsea environment using propellers which are powered with energy transmitted through the umbilical cords. AUVs are not range-limited by a physical connection to the surface, but cannot operate indefinitely because they tend to exhaust their storage batteries quickly, necessitating frequent trips to the surface for recharging. Another difference is that ROVs exchange data and commands with the surface ship via the umbilical cable, whereas AUVs exchange data and commands via wireless communications, or store data in hardware while they are submerged. In some cases, the hardware storing the data is picked up at the sea surface. AUVs carry batteries which power their propellers, carry a minimal payload and navigate only certain distances.
A further underwater vehicle, known as a glider have no embedded propulsion system, but have the ability to change buoyancy, enabling gradual ascent or descent. Energy is carried by the glider to open and close a pump which allows water in or out of the glider thus changing the buoyancy of the glider. Gliders are unable to carry payloads other than their own weight.
While ROVs, AUVs, HROVs and Gliders are capable of performing tasks which cannot be practically performed in a cost-effective manner by divers, the energy to traverse the media is carried by the vehicle or transmitted to it via a cable (ROV). Traversing of the media is carried out in ROVs, AUVs and HROVs using propellers or in the case of gliders by modifying their buoyancy. There is a need for a vertical glider robot to carry a minimum amount of energy to power only its instrumentation, but not to power its locomotion, thus improving the cost-effectiveness of these devices.
Considerable research has been done on the problems associated with recovery of undersea resources. The following are some examples. U.S. Pat. No. 3,643,736 entitled SUB SEA PRODUCTION STATION describes production of sub sea deposits through a satellite system. The system is not configured to support autonomous operations. U.S. Pat. No. 3,454,083 entitled FAIL-SAFE SUBSEA FLUID TRANSPORTATION SYSTEM describes a system for production of fluid minerals. The system includes a product gathering network having production satellites in which the gas-oil water ratios of each well are periodically tested and the flow rates are automatically controlled. U.S. Pat. No. 6,808,021 B2, entitled SUB SEA INTERVENTION SYSTEM, describes a system that is usable within sub sea wells that extend beneath the sea floor, including a station that is located on the sea floor and an underwater vehicle. The underwater vehicle is housed in the station and is adapted to service the subsea wells.